Prevent stall screw motor

The utility model relates to a prevent stall screw motor in oil and natural gas well drilling, prospecting, mine probing, development of coal -bed gas field. It includes casing, stator and rotor, wherein: protruding edge in establishing in the casing upper portion, stator upper portion is equipped with the evagination edge, protruding edge and stator evagination along the spacing cooperation of constitution axial in the casing, casing and the cooperation of stator constitution circumference rotary seal, set up spiral spline and spring assembly in the toroidal cavity between casing and stator,casing internal surface and stator surface processed respectively with spiral spline engaged with spiral spline groove structure, spring assembly upper and lower respectively with the casing in protruding edge and spiral spline support the cooperation. Prevent stall screw motor helps improvement instrument face directive efficiency, extension bit life, and compatible strong, can merge with other screw rods motor structure